<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div class="box">1</div>
    <div class="box">2</div>
    <div id="nav">
        <ul>
            <li>3</li>
            <li>4</li>
        </ul>
    </div>
    <script>
        // H5之后
        // 1. getElementsByClassName 根据类名获取某些元素集合
        var boxs = document.getElementsByClassName('box');
        console.log(boxs);

        // 2. querySelector 返回指定选择器的第一个元素对象 切记 里面的选择器要加符号 .box #nav
        var firstBox = document.querySelector('.box');
        console.log(firstBox);

        var nav = document.querySelector('#nav');
        console.log(nav);

        var li = document.querySelector('li');
        console.log(li);

        // 3. querySelectorAll 返回指定选择器的所有元素对象集合
        var allBox = document.querySelectorAll('.box');
        console.log('----', allBox);

        var lis = document.querySelectorAll('li');
        console.log('++++++', lis);
    </script>
</body>

</html>